<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div>
        <div>
            用户名  <input id="username"/>
        </div>
        <div>
            密码  <input id="userpwd"/>
        </div>
        <button id="btn">提交</button>
    </div>
</body>
<script src="jquery-1.11.3.js"></script>
<script>
    $("#username").val("abc");
    $("#userpwd").val("123")
    $("#btn").click(()=>{
        alert("提交")
    })


</script>
</html>